There are five major objectives for the Rocky Mountain Spotted Fever project on Cape Code, Massachusetts: 1) to establish the existence of acute RMSF in dogs and to characterize the clinical, immunologic, epidemiologic and serologic features of the disease in the Cape Cod dog population. 2) To locate and define the boundaries of suspected foci of ticks infected with RMSF on Cape Cod. 3) To determine the role of dogs in the transmission of RMSF to man. 4) To design models for control or prevention of RMSF on Cape Cod through dog, tick or other methods of control. 5) To design a model for the effective study and control of RMSF elsewhere in the United States. Veterinarians on Cape Cod have been enlisted in the research to send blood on dogs, sick or well. Dogs have been discovered with acute RMSF from whose blood rickettsiae have been isolated. Additionally, approximately 10% of dogs on the Cape have significant residual RMSF antibody titers. Tick studies include hemolymph tests for rickettsial-like organisms and confirmation tests with immunofluorescence.